A central challenge facing the geosciences is to bridge the gulf of time, and bring a clear reckoning of Earth history to bear on contemporary environmental problems. The driving principle behind my work is that the past is the key to the future, and understanding how Earth’s landscapes evolved as a result of environmental change throughout geologic time is critical for preparing for future climate impacts on communities and infrastructure.
Sedimentary rocks are the primary archives that document how the Earth’s air, water, and life have changed throughout geologic time. However, sediments are unreliable bookkeepers. The strata omit information at random and without warning because external factors—like rainfall on mountain hillslopes and earthquakes on continental margins—induce scale-dependent internal feedbacks that shred and buffer environmental signals.
My research program seeks to untangle noise from signal by: (1) characterizing morphodynamic feedbacks that shape landscape evolution and (2) investigating how external boundary conditions impact these feedbacks across the source-to-sink continuum. Currently, my research is advancing these lines of inquiry via four broad areas of work.
In each of these areas, I draw inspiration from strata and modern sedimentary landscapes to design targeted physical sedimentary experiments and numerical models. In this way, I apply hypothesis testing to learn how changing conditions impacted paleoenvironments, and better understand how modern landscapes might evolve in the coming centuries.
Time in the Stratigraphic Record
Earth’s history is written in sedimentary rocks, which stack layer upon layer to form strata. We can read the pages of the strata to understand Earth’s environment. However, sediments are unreliable record-keepers. The strata omit information at random and without warning because external factors—like rainfall on mountain hillslopes and earthquakes on continental margins—induce scale-dependent internal feedbacks that shred and buffer environmental signals. A major component of my research is devoted to connecting processes to preservation. Drawing inspiration from rock outcrops (like the one below in the Piceance Basin, western Colorado, USA), I conduct flume and delta tank experiments to determine what processes turn on the tape recorder, which ones turn it off, and how we can tell the difference.
Signal Propagation in River Networks
River networks are the most important conduits conveying water and sediment from the mountains to the sea. In this way, rivers can transmit signals encoded as mass fluctuations. When mountains shed more stones and sand, the open veins slowly transport that sediment downstream, and in so doing, transmit the information that something has changed in the mountains.
However, unlike telephone lines, rivers are a very noisy communication medium. At every bend along the river, signal fidelity is lost because some sediment gets deposited and left behind, and then later released all at once. This storage-and-release cycle occurs at many scales, and there are many different kinds of sediment traps in the river system.
A major focus of my research centers on understanding how sediment baffling by within-network traps scales up to distort environmenal signals propagating across the landscape.
I am currently investigating this question using computer modeling, where I can set up simulated river networks with tributary junctions and assign different rules for how impounded tributaries fill.
Water and Sediment Transport on Floodplains
People build civilizations on floodplains because they are (mostly) flat, close to reliable water sources, and make for fertile farmland. Millions upon millions of people live on them, and all risk having their home, livelihood, and community destroyed by floodwaters. To protect these communities and help them thrive, governments build levees on either side of the river that hold back the rising water.
Because flow, erosion, and deposition in floodwaters often depend on local factors (rain here, not there; a levee breach here, not there), it is challenging to establish general rules for how floodplains evolve. I am currently investigating whether hydrograph variability is a general control on floodplain sediment dispersal.
Ocean-bottom sediment transport
Water, air and ice are responsible for the majority of sedient creation, erosion, and transport on the part of Earth's surface exposed to the atmosphere. Less is known about the mechanisms of sediment transport on the ocean floor. I am actively developing a major research initiative to understand the timescales of sediment transport on continental shelves, slopes, and the abyssal plain.